Web Tools

Main Content

Inflow and Infiltration

Inflow and infiltration happens when water from the environment enters the sewage system for treatment.

York Region has two sewer systems:

Sewage system (sanitary sewer)

Storm sewer

The sewage system is designed to carry sewage to treatment plants for processing before returning it to the environment. The storm sewer prevents streets from flooding by draining and carrying excess stormwater (water from rainfall and snowmelt) to lakes and streams.

York Region and its consultant (CIVICA), in partnership with the Towns of Aurora and Newmarket are starting a project in your neighbourhood to help fix roof downspouts, sump pumps, foundation drains or other drains that are directly connected to the sanitary sewer.

Monitoring shows that high amounts of rain water, melted snow and groundwater are entering the sewer system through inflow and infiltration.

High levels of inflow and infiltration put the sewer system at risk of backups, which can lead to basement flooding. It is also very costly to have what is mostly clean water sent to the wastewater treatment plant and taking up pipe capacity.

Only those areas which are identified may be impacted by restoration work.

View frequently asked questions or copies of communication materials (PDF) which are being delivered to impacted residential areas:

Finding and reducing inflow and infiltration is a high priority. It reduces the cost of treating stormwater water as sewage, helps to maintain and extend the life of costly infrastructure and helps to ensure there is enough capacity for wastewater to move through the system.

Finding Sources of Inflow and Infiltration

York Region monitors rainfall and the sewage system to find areas with higher than expected water flow.

We may further investigate sources through forcing vegetable based, non-toxic, odourless smoke into sewer maintenance holes or adding a non-toxic dye to an upstream freshwater source believed to be contributing to inflow and infiltration.

Reducing Inflow and Infiltration

Once a source of inflow and infiltration has been found, York Region or local towns and cities inspect and repair issues in manholes and sewer lines, reducing inflow and infiltration in the community’s sewage system.

Inflow,infiltration,inflow and infiltration,I/I,I&I,I & I,sewage,sewer,waste water,storm system,sewer system,sewage system,combine system,cross connections,pipes,lateral pipes,downspouts,sump pumps,surface water,groundwater,clear waterJul 12, 2018, 10:29:14 AM EDTThe Regional Municipality of Yorken-USThe Regional Municipality of York
Inflow and Infiltration
Inflow and infiltration is a problem that increases the cost of water for residents. Learn what it is and what York Region is doing to stop it.